Spinal fusion implant

ABSTRACT

A spinal fusion implant including a body and a jacket is disclosed. The jacket includes at least two radiopaque markers extending therefrom for use in determining the position of the implant after placement between intervertebral bodies. Methods of implanting and evaluating positioning of the implant are also disclosed.

BACKGROUND OF THE INVENTION

The present invention relates to spinal surgery, namely, the fusion ofadjacent intervertebral bodies.

Back pain can be caused by many different maladies, not the least ofwhich are problems that directly impact the intervertebral disks of thespine. Typical disc issues include, inter alia, degeneration, bulging,herniation, thinning and abnormal movement. One method of treatment ofsuch disc problems that has been widely utilized in the field of spinalsurgery is a spinal fusion procedure, whereby an affected disc isremoved, and the adjacent vertebral bodies are fused together.Currently, implants, pedicle screws and the like are utilized tofacilitate the fusion.

One type of implant that has recently gained favor are so-calledstand-alone cages. These intervertebral implants effectuate spinalfusion without the need for secondary fixation through the use of, forinstance, pedicle screws. One example of such a stand-alone cage isdisclosed in U.S. Pat. No. 8,349,015 (“the '015 Patent”), the disclosureof which is hereby incorporated by reference herein. In the '015 Patent,a PEEK body is surrounded by a metallic jacket and anchors are insertedthrough both superior and inferior surfaces the implant and into theupper and lower adjacent vertebral bodies respectively.

Although stand-alone cages are successful in effectuating spine fusion,intraoperative and postoperative visualization of the implants remains achallenge. This is especially true given the advent of polymericimplants that are constructed of PEEK and therefore do not show up whenconducting standard imaging processes. Nonetheless, surgeons typicallyneed to verify proper implant position, location and rotation.

It has been known for some time to imbed radiopaque markers in polymericbodies, so that at least the markers show up on X-rays or other imagestaken of the implant. Surgeon can compare the positions of the markersto each other and/or the anatomical features of the spine to determinewhether the implant is properly placed. However, implants with such adesign require additional manufacturing efforts (i.e., imbedding themarkers in the polymeric) that are costly, time consuming and mayadversely affect the structural integrity of the implants.

Therefore, there exists a need for an improved spinal implant thatovercomes the aforementioned drawbacks.

BRIEF SUMMARY OF THE INVENTION

The present invention provides a unique design that allows forevaluation of the placement of a spinal fusion implant. In its mostbasic sense, the invention includes at least two extensions extendingfrom a jacket surrounding an implant body that are radiopaque. Theseextensions can be viewed via an imaging technique and their orientationwith respect to each other or other aspects of the implant can aid asurgeon in determining whether the implant is properly placed. Ofcourse, the specific configuration of the extensions may widely vary, ascan the specific implants themselves.

A first aspect of the present invention is an intervertebral implantincluding a body sized and shaped for placement between first and secondadjacent vertebrae, a jacket disposed around the spacer and at least tworadiopaque markers extending from the jacket to enable identification ofan orientation of the implant.

In certain embodiments of the first aspect, the implant may furtherinclude first and second anchors secured to the implant and the firstand second vertebrae. The at least two radiopaque markers may be locatedon opposite sides of the jacket. In an aligned orientation, only one ofthe at least two markers is visible from a first aspect, and when theimplant is in a misaligned orientation portions of both of the at leasttwo markers are visible from the first aspect. The body may be at leastpartially radiolucent. The at least two radiopaque markers may includefour radiopaque markers, and the four radiopaque markers may be angledwith respect to upper and lower surfaces of the implant. The jacket mayinclude two rails and the at least two radiopaque markers may extendbetween the rails. The at least two radioapque markers may betriangular.

Another aspect of the present invention is a method of determining theorientation of an implant placed between two intervertebral bodiesincluding the steps of viewing opposed radioactive markers located onfront and back sides of a jacket of the implant and determining theorientation of the implant based on the orientation of the markers. Inan aligned orientation, only a single marker is visible from a firstaspect. In a misaligned orientation, at least portions of each of themarkers are visible from the first aspect. The first aspect may be froman anterior side of a patient.

Another aspect of the present invention is a method of implanting animplant between two intervertebral bodies including the steps ofaccessing the space between the intervertebral bodies, placing theimplant between the intervertebral bodies, viewing opposed radioactivemarkers located on front and back sides of a jacket of the implant; anddetermining the orientation of the implant based on the orientation ofthe markers. In an aligned orientation, only a single marker may bevisible from a first aspect. In a misaligned orientation, at leastportions of each of the markers may be visible from the first aspect.The first aspect may from an anterior side of a patient.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the subject matter of the presentinvention and of the various advantages thereof can be realized byreference to the following detailed description in which reference ismade to the accompanying drawings in which:

FIG. 1 is a perspective view of an implant according to one embodimentof the present invention.

FIG. 2 is a top view of the implant of FIG. 1.

FIG. 3 is a side view of the implant of FIG. 1.

FIG. 4 is a front view of the implant of FIG. 1.

FIG. 5 is a side view of an implant according to another embodiment ofthe present invention.

FIG. 6 is a side view of an implant according to another embodiment ofthe present invention.

FIG. 7 is a side view of an implant according to another embodiment ofthe present invention.

FIG. 8 is a side view of an implant according to another embodiment ofthe present invention.

FIG. 9 is a side view of an implant according to another embodiment ofthe present invention.

FIG. 10 is a side view of an implant according to another embodiment ofthe present invention.

FIG. 11 is a side view of an implant according to another embodiment ofthe present invention.

FIG. 12 is a side view of an implant according to another embodiment ofthe present invention.

FIG. 13 is a side view of an implant according to another embodiment ofthe present invention.

FIG. 14 is a side view of an implant according to another embodiment ofthe present invention.

DETAILED DESCRIPTION

As shown in FIGS. 1-4, an implant 10 is disclosed that includes a PEEKbody 12 and a metallic jacket 14. Jacket 14 is sized and shaped so as tofit around an exterior of PEEK body 12, and both components includeportions of an upper channel 16 and a lower channel 18 (the latter ofwhich is best shown in FIG. 4) that are designed to accept an anchor(like anchor 120 shown in FIG. 5). This design allows for implant 10 tobe placed between adjacent intervertebral bodies and anchors tothereafter be secured to both the implant and the vertebral bodies,thereby creating a stand-alone fusion cage construct. In the particularembodiment shown in the figures of the present application, the variousimplants are designed for lateral placement between adjacent vertebralbodies. In other words, the implants are sized and shaped to be placedfrom the side of a patient and across the disc space. The particularlateral implants shown may exhibit lengths within the range of 40-60 mm,widths within the range of 18-22 mm and heights in the range of 8-18 mm.However, it is contemplated that the present invention has applicabilityto implants of many different sizes and shapes, including those designedfor placement in other orientations, e.g., anteriorly, posteriorly,posterior-laterally or the like. Depending upon the particular insertionorientation, the implants may be sized within different ranges.

PEEK body 12 includes teeth 22 on and a plurality of apertures 24through its top and bottom surfaces. The teeth aid in at least initiallysecuring the implant between adjacent vertebral bodies, while theapertures may be packed with bone graft material to allow for bone togrow between the vertebral bodies. Of course, it is contemplated thatthe implant may be designed such that teeth are not included and/or oneor more apertures may be provided. Moreover, although described as beingconstructed of PEEK, it is noted that body 12 may be constructed of manydifferent materials, including many different polymeric materials inaccordance with the present invention. It is also contemplated toconstruct body 12 of biologic materials, such as allograft bone.

Jacket 14, on the other hand, is comprised of a metallic material anddesigned such that it entirely surrounds PEEK body 12. Because jacket 14is comprised of a metallic material, it can be seen when conducting anx-ray or other imaging technique. This is in contrast to the polymericmaterial of body 12, which cannot optimally be seen in such imagingprocedures (PEEK can be seen depending upon x-ray settings). Jacket 14is shown as including end portions separated by four rails (two on eachside of the jacket), but can be of any shape sufficient to surround body12.

Jacket 14 includes four extensions 26 (two on each side of the implant)which extend toward an upper surface of implant 10. Extensions 26 areshown as being equally spaced from ends of jacket 14, as well as aboutits center. Of course, extensions 26 may be positioned at any positionon jacket 14. These structures provide specific reference points for asurgeon viewing implant 10 under an imaging process. For instance, atypical image will be taken from a front portion of a patient's body,and if implant 10 is correctly placed, extensions 26 on the front andback side of the implant will align such that only two extensions 26will be visible in the image. However, when implant 10 is not properlyaligned (e.g., rotated in one direction or the other), the image willbegin to show extensions 26 on the posterior side of the implant (i.e.,at least portions of all four extensions will show).

It is noted that other portions of jacket 14 may also aide in thedetermination of the placement of implant 10. For instance, the endportions of the implant (best shown on the left and right sides of theview of FIG. 3) can be utilized by a surgeon in a similar fashion toextensions 26. Likewise, the rails on the front and back of jacket 14can be utilized to determine whether the implant is canted toward one ofthe upper or lower intervertebral body. This canting may occur becauseof subsidence, improper bone preparation or an improper placement.Extensions 26 are oriented so that they face the upper surface ofimplant 10. This allows for a quick determination as to whether theimplant is properly oriented within the disc space. In otherembodiments, extensions 26 could be oriented such that they face thebottom of the implant, or even to one side or the other. As is bestshown in FIG. 3, body 12 may include its own radiopaque marker 28, whichcan be utilized in conjunction with extensions 26 to determine properposition of implant 10.

Of course, although described as being constructed of a metallicmaterial, it is noted that jacket 14 may be constructed of manydifferent types of materials, including different metals. In fact, theentirety of jacket 14 need not be radiopaque, although it is in thevarious embodiments of the present invention. Rather, extensions 26 maybe the sole portion of jacket 14 constructed of radiopaque material,thereby allowing visualization during an imaging process.

FIGS. 5-13 disclose several additional embodiment implants in accordancewith the present invention. For ease of reference, like referencenumerals are utilized for similar elements of the implants, albeitwithin different 100-series of numbers. For instance, FIG. 5 depicts animplant 110 that includes a PEEK body 112, a jacket 114 and extensions126. Extensions 126 are wider and include less of a distancetherebetween than that of extensions 26 of implant. This design mayallow for an easier determination of misalignment of implant 110, as thespace between extensions 126 simply closes when viewed from the anteriorside of the patient. Otherwise, extensions 126 are largely similar tothose of implant 10.

Implant 210 of FIG. 6 includes a single extension 226 on each side.Therefore, instead of four extensions, implant 210 includes two. In theparticular embodiment shown, extensions 226 are oriented at a center ofimplant 210, but could be positioned in other locations on jacket 214.FIG. 7 depicts an implant 310 in which extensions 326 extend betweenrails of jacket 314 on each side of the implant. This design not onlyprovides a similar functionality to the foregoing implants, but alsopotentially adds stability to the construct of jacket 314. FIG. 8depicts a design similar to implant 310, but with two extensions 426extending between rails on both sides of the implant. Therefore, insteadof the two extensions shown in FIG. 7, the embodiment of implant 410includes four. Implant 510 of FIG. 9 includes four angled extensions 526that extend between the rails. Again, the functionality of extensions526 otherwise remains the same.

FIG. 10 depicts an embodiment in which instead of extensions, jacket 614includes holes 626 formed in the rails thereof. Holes 626 provide thesurgeon with similar viewing capabilities in an imaging process as theabove-discussed embodiments do. For instance, a properly placed implantwill show two complete holes extending through the jacket, whereas atilted or otherwise improperly placed implant will show the holesomewhat obscured. FIG. 11 depicts an embodiment in which eight holes726 are included in jacket 714. FIG. 12 depicts a design in whichinstead of holes, jacket 814 includes necked down sections 826 that canbe utilized in a similar fashion to the holes.

Implant 910 of FIG. 13 includes triangular extensions 926 that can beutilized in a similar fashion as is discussed above in connection withimplant 10. The triangular shape of extensions 926 allow for them toextend to a height on implant 910 that is possible with theabove-discussed extensions. Moreover, the center area of extensions 926allow for better visualization of the remainder of implant 910. This canbe utilized to, among other things, better assess the amount of bonegrowth that has occurred through body 912 of an implanted implant 910.Finally, implant 1010 of FIG. 14 depicts and embodiment similar to thatof FIG. 7. However, instead of extending towards only one of the upperor lower surface of the implant, extensions 1026 extend towards both.This design may allow for an easier determination of where those upperand lower surfaces are in an implanted implant.

In one embodiment of the invention, an intervertebral implant comprises:

a body sized and shaped for placement between first and second adjacentvertebrae;

a jacket disposed around the spacer; and

at least two radiopaque markers extending from the jacket to enableidentification of an orientation of the implant.

In another embodiment of the invention, a method of determining theorientation of an implant placed between two intervertebral bodiescomprises the steps of:

viewing opposed radioactive markers located on front and back sides of ajacket of the implant; and

determining the orientation of the implant based on the orientation ofthe markers,

wherein in an aligned orientation, only a single marker is visible froma first aspect.

Although the invention herein has been described with reference toparticular embodiments, it is to be understood that these embodimentsare merely illustrative of the principles and applications of thepresent invention. It is therefore to be understood that numerousmodifications may be made to the illustrative embodiments and that otherarrangements may be devised without departing from the spirit and scopeof the present invention as defined by the appended claims.

The invention claimed is:
 1. An intervertebral implant comprising: abody sized and shaped for placement between first and second adjacentvertebrae, the body having an outer dimension; a jacket having an innerdimension larger than the outer dimension and disposed around and alongan outer perimeter of the body, the jacket including first and secondrails extending along a first lateral side of the jacket and third andfourth rails extending along a second lateral side of the jacket, thefirst and second laterals sides being opposite; and at least tworadiopaque markers extending from and connected to the jacket to enableidentification of an orientation of the implant, a first markerextending only from the first rail to the second rail on the firstlateral side and a second marker extending only from the third rail tothe fourth rail on the second lateral side.
 2. The implant of claim 1,further comprising first and second removable anchors secured to theimplant and configured to be secured to the first and second vertebrae.3. The implant of claim 2, wherein the first removable anchor is securedto an upper channel and the second removable anchor is secured to alower channel of the body.
 4. The implant of claim 1, wherein when theimplant is in an aligned orientation, only one of the at least twomarkers is visible from a first aspect, and when the implant is in amisaligned orientation portions of both of the at least two markers arevisible from the first aspect.
 5. The implant of claim 1, wherein thebody is at least partially radiolucent.
 6. The implant of claim 1,wherein the at least two radiopaque markers further include a thirdmarker extending from the first rail to the second rail and a fourthmarker extending from the third rail to the fourth rail.
 7. The implantof claim 6, wherein the four radiopaque markers are angled with respectto upper and lower surfaces of the implant.
 8. The implant of claim 1,wherein an upper surface and a bottom surface of the body have teethconfigured to secure the implant to the first and second vertebrae. 9.The implant of claim 1, wherein the body includes one or more apertures.10. The implant of claim 9, wherein the apertures contain bone graftmaterial.
 11. The implant of claim 1, wherein the jacket furthercomprises two end portions attached at opposite ends of the two rails.12. The implant of claim 1, wherein the first and second rails extend ina medial-lateral direction when the implant is implanted.